1. Field of the Invention
The present invention related to an optical transceiver, in particular, the invention relates to a structure of the optical transceiver that secures the heat dissipating capability of an optical subassembly installed within the optical transceiver.
2. Related Prior Art
The optical transceiver can operate in the optical transmission and the optical reception by inserting an optical connector into an optical receptacle of the transceiver to couple an optical fiber in the optical connector in optical with an optical devices installed in the transceiver. This optical coupling may be performed by inserting a ferrule provided in a tip of the optical fiber into a sleeve accompanied with the optical device.
The United States Patent, U.S. Pat. No. 6,884,997, has disclosed an optical transceiver, which integrally builds a housing for enclosing a transmitting optical subassembly (TOSA), a receiving optical subassembly (ROSA), and a substrate, with an optical receptacle for receiving an optical connector. The optical connector widely used in the optical communication apparatus has a standard that strictly rules, for instance, the position of the ferrule within the connector housing and the geometrical relation between the ferrule and the sleeve mating with the ferrule in order to couple the optical fiber attached to the connector with the optical device conjunct with the sleeve.
On the other hand, in the subassembly including the sleeve and the package that holds the sleeve and installs the optical device therein, the positional relation between the sleeve and the optical device is aligned by practically (1) inserting the optical fiber into the sleeve, (2) guiding light within the optical fiber and (3) aligning the position of the sleeve with respect to the optical device. This optical alignment generally does not take the positional relation between the sleeve and the package into account. For example, when the package has the so-called butterfly type with a box shape and the sleeve is attached to one side wall of the package, the precise position of the sleeve in the side wall thereof is taken no thought. The optical alignment between the sleeve, namely, the optical fiber, and the device has the first priority. Accordingly, the sleeve is occasionally attached to a point in the side wall offset from the designed position. Thus, when such subassembly is installed within the transceiver, although the sleeve thereof is precisely positioned to the receptacle, which is formed as a part of the transceiver housing, the package of the subassembly is not always positioned to the housing accurately.
The optical transceiver for the long reach communication or for the wavelength division multiplex (WDM) communication is necessary to control a temperature of the laser diode (LD) to stabilize the emission wavelength thereof. Therefore, the subassembly applied in such optical transceivers installs a thermoelectric controller such as Peltier device within the package. The Peltier device with two plates has a feature that, when one plate thereof is cooled down, the other plate is heated up. Since the LD generates heat due to the current flowing, the LD is mounted on the plate to be cooled down, while the other plate is attached to the package, generally the bottom of the package to radiate heat outward. Therefore, the bottom of the package is necessary to come in contact to some objects to enhance the heat dissipating function.
The pluggable transceiver, which is one type of the optical transceiver and has an essential feature to be inserted into or removed from the cage, is unable to provide a heat dissipating mechanism such as heat radiating fin in the housing because such mechanism may interfere the insertion/extraction function of the transceiver with to the cage. Only the housing body itself is left to dissipate heat from the inside thereof to the outside. Accordingly, in the transceiver installing the subassembly with the box-shaped package and the thermoelectric cooler therein, one outer wall, to which the thermoelectric cooler is attached, is necessary to fit to the housing of the transceiver.
However, as mentioned previously, the position of the subassembly, in particular, the package thereof is not always set in the predetermined position within the housing. Because the optical axis of the subassembly, namely, the position of the sleeve is first determined with respect to the housing, the package of the subassembly occasionally causes a gap to the housing body, or is fit to the housing body as inducing the mechanical stress in the connecting portion between the sleeve and the package. The former case is unable to show the good heat transfer therebetween, while the latter case brings the degradation in the reliability.
The present invention provides a new arrangement of the optical receptacle and the optical subassembly to the housing body of the transceiver, in which the optical coupling between the optical fiber inserted into the optical receptacle and the subassembly may be maintained and the good heat dissipating function of the subassembly may be kept.